Note: This is a seattlepi.com reader blog. It is not written or edited by the P-I. The authors are solely responsible for content. E-mail us at newmedia@seattlepi.com if you consider a post inappropriate.

Viaduct: Next major steps in tunnel construction

Computer-aided illustrations help give some idea of what Seattle's waterfront will look like after the Alaskan Way Viaduct is replaced with a tunnel.
This is the view now to the north from the viaduct at South Royal Brougham Way. (Photo provided by WSDOT) less

Computer-aided illustrations help give some idea of what Seattle's waterfront will look like after the Alaskan Way Viaduct is replaced with a tunnel.
This is the view now to the north from the viaduct at ... more

Image 2 of 13

Future: View to the north from new Highway 99 at South Royal Brougham Way. (Photo provided by WSDOT)

Future: View to the north from new Highway 99 at South Royal Brougham Way. (Photo provided by WSDOT)

Image 3 of 13

Now: View to the southeast down Railroad Way South from Alaskan Way. (Photo provided by WSDOT)

Now: View to the southeast down Railroad Way South from Alaskan Way. (Photo provided by WSDOT)

Image 4 of 13

Future: View to the southeast down Railroad Way South from Alaskan Way. (Photo provided by WSDOT)

Future: View to the southeast down Railroad Way South from Alaskan Way. (Photo provided by WSDOT)

Image 5 of 13

Now: View to the west from University Street at First Avenue. (Photo provided by WSDOT)

Now: View to the west from University Street at First Avenue. (Photo provided by WSDOT)

Image 6 of 13

Future: View to the west from University Street at First Avenue. (Photo provided by WSDOT)

Future: View to the west from University Street at First Avenue. (Photo provided by WSDOT)

Image 7 of 13

Now: View to the south down Alaskan Way from Union Street (Waterfront Park. (Photo provided by WSDOT)

Now: View to the south down Alaskan Way from Union Street (Waterfront Park. (Photo provided by WSDOT)

Image 8 of 13

Future: View to the south down Alaskan Way from Union Street (This conception doesn't show a new waterfront park).

Future: View to the south down Alaskan Way from Union Street (This conception doesn't show a new waterfront park).

Image 9 of 13

Now: View to the north from Union Street (Waterfront Park). (Photo provided by WSDOT)

Now: View to the north from Union Street (Waterfront Park). (Photo provided by WSDOT)

Image 10 of 13

Future: View to the north from Union Street (Waterfront Park). (Photo provided by WSDOT)

Future: View to the north from Union Street (Waterfront Park). (Photo provided by WSDOT)

Image 11 of 13

Now: View to the south from Victor Steinbrueck Park. (Photo provided by WSDOT)

Now: View to the south from Victor Steinbrueck Park. (Photo provided by WSDOT)

Image 12 of 13

Future: View to the south from Victor Steinbrueck Park. (Photo provided by WSDOT)

Future: View to the south from Victor Steinbrueck Park. (Photo provided by WSDOT)

Image 13 of 13

Viaduct: Next major steps in tunnel construction

1 / 13

Back to Gallery

As Seattle’s tunnel referendum last month made us painfully aware, the City Council still has to give the state a final notice to proceed before the project moves ahead full bore.

Thus, the City Council’s special committee on the viaduct is scheduled to meet Tuesday to set that process in motion. The committee will hear from officials on the state’s viaduct team, who will report on the environmental review process and the federal approval of the project in August. The meeting is scheduled at 2:30 p.m. at City Hall. After that, the council will hold another public meeting in a week or a two to give the final thumbs-up.

With the $1.9 billion tunnel project moving ahead, start looking for more activity at the site of the tunnel’s south portal — a large gravel lot in Sodo where the First Avenue off-ramp touches down west of the sports stadiums. More trailers and heavy machinery soon will be moving in, said Chris Dixon, deputy project executive for the tunnel’s joint-venture contractor, Seattle Tunnel Partners.

Roughly, here’s what else we can expect over the next year:

WSDOT announced last week the viaduct will be closed from Oct. 21 to Oct. 31 to demolish a large section of the structure in Sodo. Crews will tear down that section to make way for a detour between a new highway through Sodo and the central viaduct along the waterfront. The rest of the Sodo section will be torn down by next year, while the central waterfront section will remain open until a new highway tunnel opens in late 2015 or early 2016.

Excavating and piling will start later this year at the site of the tunnel’s south portal, although it may not be very noticeable, Dixon said.

Early in 2012, ground-stabilization work will start along the viaduct and buildings at heightened risk of settlement during tunnel construction. That work will entail installing “micropile walls,” which are constructed by drilling into the ground and installing a series of six-inch pipes filled with grout or a concrete mixture, Dixon said. “If we have any loose ground along the tunnel path that could result in settlement, that zone is confined between the micropile wall and the tunnel. It never makes it over to the structure,” he said.

The work could take three to four weeks at each site. Crews will need room to operate, so there could be lane closures or blocked access to curbside parking at locations where work is underway. In the beginning, crews will be working near the Al Boccalino Restaurant on Yesler Way in Pioneer Square. At the north portal, they’ll be doing mitigation near a few law offices and the Travel Lodge on Aurora Avenue North, he said.

Ordering the gigantic tunnel-boring machine from contractor Hitachi Zosen is under way. The boring machine won’t be shipped to Seattle until March 2013. Then it will be assembled, tested and commissioned before tunneling beneath downtown Seattle starts in June 2013. Digging the 1.7-mile long, 57-foot diameter tunnel will take about 16 months.

Seattle Tunnel Partners includes New York-based Dragados USA, whose parent company is ACS of Spain; Tutor-Perini out of California, and HNTB Corp., which is headquartered in Kansas City and has a Bellevue office. Dixon has 35 years in the tunneling industry in the U.S. and internationally, he said. Before coming to the Seattle project, he was the construction manager on the ARC Tunnel project — a new subway between New Jersey and New York — that New Jersey Gov. Chris Christie halted last year due to concerns about costs.

“I’m really happy to be in Seattle. We have a very good team. WSDOT is a very good client. The project is moving forward very nicely and I’m very excited about it,” he said. “This really is a landmark project for many reasons — one is the large diameter size of the tunnel.”

Note: This is a seattlepi.com reader blog. It is not written or edited by the P-I. The authors are solely responsible for content. E-mail us at newmedia@seattlepi.com if you consider a post inappropriate.